What is a software plc?

A Software PLC is a software version of a programmable logic controller (PLC). It combines the functions of conventional PLCs with those of data loggers, communication gateways, and other elements such as human-machine interfaces (HMI) and web servers. In the early days of SoftPLC, it was common to use industrial PC hardware as a platform, initially with Windows.

Nowadays, most installations use real-time OS (Linux, VX Works, FreeRTOS, QNX…)

The strengths of software PLC

  • Time to market: It is as easy to transform a board into a PLC (2 days of integration) as to add a communication protocol. The development of the board and the application can be done in parallel.   
  • Flexibility: Thanks to the sources, it is possible to change CPU and/or OS while keeping the applications, so you can address several markets.  
  • Openness: The softPLC is a simple application brick, it works with other applications (motion, HMI, gateway, business application, …)  
  • Standards compliance: The soft PLC allows the use of the 5 IEC61131 languages and the certification is simplified thanks to the respect of the protocols standards (IEC61850, IEC101/104, DNP3…).  
  • Financial: A single investment is enough to create an unlimited number of applications and to control the price of its products throughout their life cycle. Moreover, you have the possibility to invest exclusively in the protocols you need.   
  • Security: The PLC software provider provides security sources and updates to allow you to comply with the latest market standards, allowing you to focus exclusively on your business. 
  • Performance: The same logic engine can run on low performance hardware (e.g. 128 KB RAM) or on powerful servers managing up to 500 000 variables.   
  • Product differentiation: In addition to bringing the PLC function to your products, the customization will be optimal with for example the addition of functionalities like HMI, motion control, business application, gateway…    


For many years, the control systems market has seen the proliferation of a variety of programming languages and development environments, different for each manufacturer.  

IEC 61131 standardizes the technology of programmable controllers and covers equipment requirements, programming languages, operating guidelines, communications and functional safety. 

The third part of IEC 61131 (IEC 61131-3) deals with the programming languages used in programmable controllers, of which there are 5.  

IEC 61131-3 defines a series of functions and data types that must be supported by all compliant PLCs. The functions are the building blocks of all programs and include arithmetic operations (addition, subtraction, etc.), Boolean logic (AND, OR, NOT, etc.) and programming structures such as loops, comparisons and decisions.  

One of the results of the adoption of IEC61131 was the recognition that the software and hardware elements of programmable logic controllers could be considered separately, giving rise to the concept of Software PLC, or virtual PLC 

Safety and Security Concerns – software PLC

Safety and security will always be a major concern for any automation system component. Misconceptions about the safety and security of SoftPLCs are primarily a result of early solutions running on non-deterministic operating systems. It is possible to develop a resilient, safe and secure solution using SoftPLC technology, which is done by almost all manufacturers.  

One of the advantages of SoftPLC solutions is that hardware and operating system choices can be made independently, depending on security and safety requirements.  

In addition, some SoftPLC solutions have even developed variations that can be integrated by OEMs into systems intended for IEC61508 (safety) certification. They do this by reducing the feature set, removing functions that could create safety risks and developing the runtime itself using approved methods. 

Synthesis on PLC softwares

A lot has changed in the 20 years since the IEC61131-3 standard was created, and the majority of popularconventionalPLCs work with SoftPLC technology. As with any solution choice, the requirements should determine the answer, but SoftPLC-based solutions should be considered in any thinking. 

The strengths of our soft plc straton software

  • Reactivity of our support service 
  • Intuitive and ergonomic editor   
  • Control of the product developments throughout the life cycle and the induced costs   
  • The same dev kit allows to produce its own runtimes for any CPU and any OS (even without OS)  
  • straton offers customized developments to meet the expectations of your customers and your market   
  • The straton software is updated every year with new features in order to guarantee the use of the latest standards and technologies.   
  • STRATON AUTOMATION is part of the international group COPA-DATA  
  • With an expertise of more than 20 years, we have the capacity to accompany you in all your automation projects   

Test the straton software for free

Subscribe to our quarterly newsletter so you don't miss any news!